Middle frame, preparation method thereof and electronic device

Abstract

This application provides a mid-frame, its manufacturing method, and an electronic device. The mid-frame of this application includes: a frame body having peripheral side surfaces, the frame body having a yield strength ranging from 480 MPa to 510 MPa; and an oxide film disposed on the peripheral side surfaces of the frame body, the oxide film having a thickness ranging from 9.3 μm to 12.1 μm. The mid-frame of this application exhibits high yield strength and good corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of electronics, specifically to a mid-frame, its manufacturing method, and an electronic device. Background Technology

[0002] The mid-frames of electronic devices such as mobile phones and tablets require high strength and good corrosion resistance; however, as 3C electronic products become thinner and lighter, even higher strength requirements are placed on the mid-frames. Current mid-frame technologies struggle to simultaneously meet the requirements of higher yield strength and better corrosion resistance. Summary of the Invention

[0003] This application provides a middle frame with high yield strength and good corrosion resistance.

[0004] A first aspect of this application provides a mid-frame, which includes:

[0005] A frame body having peripheral surfaces, the frame body having a yield strength ranging from 480 MPa to 510 MPa; and

[0006] An oxide film is disposed on the peripheral side surface of the frame body, and the thickness of the oxide film ranges from 9.3 μm to 12.1 μm.

[0007] A second aspect of this application provides a method for preparing a middle frame, comprising:

[0008] Provide castings;

[0009] The casting is molded to obtain a first intermediate product;

[0010] The first intermediate product is subjected to aging treatment to obtain a second intermediate product; wherein the aging treatment includes a first-level aging treatment and a second-level aging treatment, the temperature of the second-level aging treatment being higher than the temperature of the first-level aging treatment; and

[0011] The second intermediate product is anodized to obtain the middle frame, wherein the middle frame includes a frame body and an oxide film, the frame body has a peripheral side surface, the oxide film is disposed on the peripheral side surface of the frame body, the yield strength of the frame body is in the range of 480 MPa to 510 MPa, and the thickness of the oxide film is in the range of 9.3 μm to 12.1 μm.

[0012] A third aspect of this application provides an electronic device comprising:

[0013] Display screen;

[0014] The mid-frame described in the first aspect of this application or the mid-frame prepared by the method described in the second aspect of this application is used to support the display screen; and

[0015] A processor is mounted on the mid-frame and electrically connected to the display screen for controlling the display screen to perform a display.

[0016] The mid-frame of this application embodiment includes a frame body and an oxide film. The yield strength of the frame body ranges from 480 MPa to 510 MPa. The oxide film is disposed on the peripheral side surface of the frame body, and the thickness of the oxide film ranges from 9.3 μm to 12.1 μm. This results in a mid-frame with high yield strength, allowing it to be made thinner. When applied to electronic devices, the mid-frame can achieve a lighter and thinner design while meeting the mechanical strength requirements of the electronic device. Furthermore, the oxide film of this application provides the mid-frame with good corrosion resistance, enabling it to withstand longer use. The thinner oxide film also makes it less prone to peeling off under high temperatures or external forces, thus improving the lifespan of the mid-frame and enhancing the user experience. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the mid-frame structure of an embodiment of this application.

[0019] Figure 2 It is the middle frame edge of an embodiment of this application Figure 1 A schematic diagram of a partial cross-sectional structure along the AA direction.

[0020] Figure 3 This is a schematic flowchart of a method for preparing the middle frame according to an embodiment of this application.

[0021] Figure 4 This is a schematic flowchart of the homogenization process according to an embodiment of this application.

[0022] Figure 5 This is a schematic flowchart of the molding process according to an embodiment of this application.

[0023] Figure 6 These are transmission electron microscope (TEM) images of the inner crystal of the first intermediate state products of Examples 1 to 7 of this application after primary aging.

[0024] Figure 7 These are transmission electron microscope (TEM) images of grain boundaries of the first intermediate state products of Examples 1 to 7 of this application after primary aging.

[0025] Figure 8 These are transmission electron microscope (TEM) images of the inner crystal of the second intermediate state products (i.e., after secondary aging) of Examples 1 to 7 of this application.

[0026] Figure 9 These are transmission electron microscope (TEM) images of the grain boundaries of the second intermediate state products (i.e., after secondary aging) of Examples 1 to 7 of this application.

[0027] Figure 10 This is a schematic diagram of the anodizing process according to an embodiment of this application.

[0028] Figure 11 This is an optical microscope image of the cross-section of the middle frame of Embodiment 1 of this application.

[0029] Figure 12 This is an optical microscope image of the cross-section of the middle frame of Comparative Example 1 of this application.

[0030] Figure 13 This is a schematic diagram of the structure of an electronic device according to an embodiment of this application.

[0031] Figure 14 This is a partial exploded structural diagram of an electronic device according to an embodiment of this application.

[0032] Figure 15 This is a circuit block diagram of an electronic device according to an embodiment of this application.

[0033] Explanation of reference numerals in the attached figures:

[0034] 100-Mid-frame, 10-Frame body, 11-Side perimeter, 20-Oxide film, 300-Electronic device, 310-Display screen, 330-Processor, 340-Housing, 341-Light-transmitting part, 350-Memory, 370-Camera module. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0036] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0037] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0038] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0039] The mid-frames of electronic devices such as mobile phones and tablets require high strength and good corrosion resistance; however, as 3C electronic products become thinner and lighter, even higher strength requirements are placed on the mid-frames. Current mid-frame technologies struggle to simultaneously meet the requirements of higher yield strength and better corrosion resistance.

[0040] Please see Figure 1 and Figure 2 This application provides a middle frame 100, which includes: a frame body 10 and an oxide film 20. The frame body 10 has a peripheral side surface 11, and the yield strength of the frame body 10 ranges from 480 MPa to 510 MPa. The oxide film 20 is disposed on the peripheral side surface 11 of the frame body 10, and the thickness of the oxide film 20 ranges from 9.3 μm to 12.1 μm.

[0041] In the embodiments of this application, when the numerical range a to b is involved, unless otherwise specified, the numerical value can be any value between a and b, including the endpoint value a and the endpoint value b.

[0042] The mid-frame 100 of this application can be applied to portable electronic devices such as mobile phones, tablets, laptops, desktop computers, smart bracelets, smartwatches, e-readers, and game consoles, serving as the mid-frame 100 of the electronic device to support the display screen and internal electronic components of the electronic device.

[0043] It should be noted that the peripheral side 11 of the frame body 10 refers to the middle frame 100 that is exposed on the surface of the electronic device when applied to the electronic device.

[0044] Optionally, the oxide film 20 is an anodic oxide film.

[0045] Optionally, the oxide film 20 has a porous structure.

[0046] Specifically, the yield strength of the frame body 10 can be, but is not limited to, 480 MPa, 485 MPa, 490 MPa, 495 MPa, 500 MPa, 505 MPa, 510 MPa, etc. If the yield strength of the frame body 10 is too low, it is not conducive to making the middle frame 100 thinner; if the yield strength of the frame body 10 is too high, it is difficult to achieve the material for the middle frame 100, or if a material with a higher yield strength can be achieved, its corrosion resistance is low, making it difficult to achieve both corrosion resistance and other properties.

[0047] Furthermore, the yield strength of the frame body 10 ranges from 490 MPa to 510 MPa. This allows the middle frame 100 to be made thinner and gives the frame body 10 higher corrosion resistance.

[0048] The yield strength of this application was measured in accordance with GB / T 16865-2023 Tensile test specimens and methods for wrought aluminum, magnesium and their alloy processed articles.

[0049] Specifically, the thickness of the oxide film 20 can be, but is not limited to, 9.3 μm, 9.5 μm, 9.8 μm, 10 μm, 10.3 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.5 μm, 11.8 μm, 12.0 μm, 12.1 μm, etc. If the oxide film 20 is too thin, the corrosion resistance of the middle frame 100 will be reduced; if the oxide film 20 is too thick, the risk of the oxide film 20 falling off when the middle frame 100 is subjected to external force will increase.

[0050] The mid-frame 100 of this application embodiment includes a frame body 10 and an oxide film 20. The yield strength of the frame body 10 ranges from 480 MPa to 510 MPa. The oxide film 20 is disposed on the peripheral side surface 11 of the frame body 10, and the thickness of the oxide film 20 ranges from 9.3 μm to 12.1 μm. This results in the mid-frame 100 having a high yield strength, allowing it to be made thinner. When the mid-frame 100 is applied to electronic devices, it allows for a thinner and lighter design while still meeting the mechanical strength requirements of the electronic devices. Furthermore, the oxide film 20 provides the mid-frame 100 with good corrosion resistance, enabling it to withstand longer use. The thinner oxide film 20 also makes it less prone to peeling off under high temperatures or external forces, thus improving the service life of the mid-frame 100 and enhancing the user experience.

[0051] In some embodiments, the frame body 10 is made of aluminum alloy. The oxide film 20 formed after anodizing of the aluminum alloy has good corrosion resistance and high brightness, thus giving the middle frame 100 both high corrosion resistance and a good appearance. In addition, aluminum alloy also has high yield strength, which can better meet the mechanical strength requirements of electronic devices for the middle frame 100.

[0052] For example, the frame body 10 is a 7-series aluminum alloy frame body. The 7-series aluminum alloy has a higher yield strength, which allows the middle frame 100 to be made thinner, which is beneficial to the thinning of the middle frame 100; in addition, this application designs the composition, process steps and process conditions of the 7-series aluminum alloy so that the oxide film 20 formed after the 7-series aluminum alloy is anodized has high corrosion resistance.

[0053] Optionally, the aluminum alloy includes grains and a second phase, the second phase including a precipitation strengthening phase and a grain boundary phase, the precipitation strengthening phase being distributed within the grains and the grain boundary phase being distributed at the grain boundaries; the average grain size of the precipitation strengthening phase is in the range of 10 nm to 20 nm.

[0054] A grain is a small, irregularly shaped crystal that makes up a polycrystalline material, and each grain is sometimes composed of several subgrains with slightly different orientations. In aluminum alloys, a grain refers to the crystal structural unit within the alloy.

[0055] The term "second phase" refers to all other phases in a material that are distinct from the matrix phase. They are generally discontinuously distributed within the matrix phase.

[0056] The term "intragranular" refers to the region inside a grain, excluding the grain boundary.

[0057] The term "grain boundary" refers to the boundary between grains, which is the junction between two or more grains.

[0058] Understandably, a second phase is dispersed both within the crystal and at the grain boundaries.

[0059] Optionally, the precipitation-enhancing phase may be, but is not limited to, a MgZn2 precipitation-enhancing phase.

[0060] Specifically, the average particle size of the precipitated strengthening phase can be, but is not limited to, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, and 20 nm. If the average particle size of the precipitated strengthening phase is too small, the corrosion resistance of the frame body 10 and the oxide film 20 is improved, but the yield strength of the frame body 10 is reduced. If the average particle size of the precipitated strengthening phase is too large, the yield strength of the frame body 10 is improved, but the corrosion resistance of the frame body 10 and the oxide film 20 is reduced. Therefore, when the average particle size of the precipitated strengthening phase is between 10 nm and 20 nm, the middle frame 100 can have both high yield strength and high corrosion resistance.

[0061] Furthermore, the average particle size of the precipitated strengthening phase ranges from 10 nm to 15 nm. This allows the middle frame 100 to have both higher yield strength and higher corrosion resistance.

[0062] In this embodiment, by controlling the size of the precipitation-strengthened phase in the frame body 10, the middle frame 100 can have higher yield strength and higher corrosion resistance.

[0063] In some embodiments, the average size of the grain boundary phase ranges from 30 nm to 50 nm.

[0064] Specifically, the average size of the grain boundary phase can be, but is not limited to, 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, 42nm, 44nm, 46nm, 48nm, 50nm, etc.

[0065] In this embodiment, if the average size of the grain boundary phase is too small, the spacing between the grain boundary phases is small, which reduces the corrosion resistance of the middle frame 100. If the average size of the grain boundary phase increases, the spacing between the grain boundary phases increases, which increases the corrosion resistance of the middle frame 100. However, if the average size of the grain boundary phase is too large, it increases the difficulty of manufacturing the frame body 10.

[0066] In some embodiments, the spacing between two adjacent grain boundary phases ranges from 30 nm to 60 nm.

[0067] Specifically, the spacing between two adjacent grain boundary phases can be, but is not limited to, 30nm, 32nm, 34nm, 36nm, 38nm, 40nm, 42nm, 44nm, 46nm, 48nm, 50nm, 52nm, 54nm, 56nm, 58nm, 60nm, etc.

[0068] In this embodiment, if the spacing between two adjacent grain boundary phases is too small, the corrosion resistance of the middle frame 100 will be reduced; increasing the spacing between two adjacent grain boundary phases can improve the corrosion resistance of the middle frame 100, but it increases the difficulty of manufacturing the frame body 10.

[0069] In some embodiments, the number density of the second phase ranges from 0.9 × 10⁻⁶. 4 μm -2 Up to 8.7×10 4 μm -2 .

[0070] Specifically, the number density of the second phase can be, but is not limited to, 0.9 × 10⁻⁶. 4 μm -2 1.0×10 4 μm -2 1.1×10 4 μm -2 1.3×10 4 μm -2 1.5×10 4 μm -2 2×10 4 μm -2 3×10 4 μm -2 4×10 4 μm -2 5×10 4 μm -2 6×10 4 μm -2 7×10 4 μm -2 8×10 4 μm -2 8.5×10 4 μm -2 8.7×10 4 μm -2 wait.

[0071] Understandably, the number of second phases per square micrometer on the transmission electron microscope image of the frame body 10 is 0.9 × 10⁻⁶. 4 Up to 8.7 × 10 4 indivual.

[0072] In this embodiment, if the quantity density of the second phase is too low, the yield strength of the frame body 10 will be too low. If the quantity density of the second phase is too high, since the oxide film 20 is obtained by anodizing the frame body 10, the corrosion resistance of the middle frame 100 will be reduced.

[0073] In some embodiments, the raw material components of the frame body 10 include, by mass fraction: 5.8% to 6.5% Zn (zinc), 2% to 2.5% Mg (magnesium), 0.1% to 0.5% Cu (copper), 0.1% to 0.3% Mn (manganese), and the balance Al (aluminum).

[0074] Specifically, the mass fraction of zinc in the raw material composition of the frame body 10 can be, but is not limited to, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, etc. If the zinc content in the raw material composition of the frame body 10 is too low, the yield strength of the frame body 10 will be reduced; if the zinc content in the raw material composition of the frame body 10 is too high, the corrosion resistance of the frame body 10 will be reduced, making the oxide film 20 prone to peeling off.

[0075] Specifically, the mass fraction of magnesium in the raw material composition of the frame body 10 can be, but is not limited to, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, etc. If the magnesium content in the raw material composition of the frame body 10 is too low, the yield strength of the frame body 10 will be reduced; if the magnesium content in the raw material composition of the frame body 10 is too high, the corrosion resistance of the frame body 10 will be reduced, making the oxide film 20 prone to peeling off.

[0076] Specifically, the mass fraction of copper in the raw material composition of the frame body 10 can be, but is not limited to, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0077] Specifically, the mass fraction of manganese in the raw material components of the frame body 10 can be, but is not limited to, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0078] In this embodiment, by designing the raw material composition of the frame body 10, the middle frame 100 has higher yield strength and better corrosion resistance, and its oxide film 20 is less likely to peel off after long-term use.

[0079] Optionally, the raw material composition of the frame body 10 further includes, by mass fraction: 0.01% to 0.1% Si (silicon), 0.005% to 0.05% Ti (titanium), and 0.01% to 0.2% Fe (iron).

[0080] Understandably, in this embodiment, the raw material components of the frame body 10, by mass fraction, include: 5.8% to 6.5% Zn (zinc), 2% to 2.5% Mg (magnesium), 0.1% to 0.5% Cu (copper), 0.1% to 0.3% Mn (manganese), 0.01% to 0.1% Si (silicon), 0.005% to 0.05% Ti (titanium), 0.01% to 0.2% Fe (iron), and the balance Al (aluminum).

[0081] Specifically, the mass fraction of silicon in the raw material composition of the frame body 10 can be, but is not limited to, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, etc.

[0082] Specifically, the mass fraction of titanium in the raw material composition of the frame body 10 can be, but is not limited to, 0.005%, 0.008%, 0.01%, 0.02%, 0.04%, 0.05%, etc.

[0083] Specifically, the mass fraction of iron in the raw material composition of the frame body 10 can be, but is not limited to, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, etc.

[0084] In this embodiment, by adding silicon, titanium and iron to the raw material composition of the frame body 10, the middle frame 100 can have higher yield strength and better corrosion resistance, and its oxide film 20 is less likely to peel off after long-term use.

[0085] In some embodiments, the Vickers hardness of the oxide film 20 ranges from 300 HV to 450 HV. Specifically, the Vickers hardness of the oxide film 20 can be, but is not limited to, 300 HV, 320 HV, 340 HV, 360 HV, 380 HV, 400 HV, 420 HV, 440 HV, 450 HV, etc. If the Vickers hardness of the oxide film 20 is too low, the wear resistance and corrosion resistance of the middle frame 100 will be reduced; if the Vickers hardness of the oxide film 20 is too high, higher requirements will be placed on the materials and processes, and it may even be difficult to achieve in terms of materials and processes.

[0086] The hardness of the oxide film 20 in this application was measured according to GB / T 4340.1-2024 Metallic materials Vickers hardness test - Part 1: Test method.

[0087] Optionally, the middle frame 100 is subjected to a copper salt spray at a temperature of 25°C and a pH value of 3.0 to 3.1 for a corrosion resistance time of 48 hours or more.

[0088] Understandably, the middle frame 100 was subjected to copper salt spray corrosion at 25°C and a pH of 3.0 to 3.1 for more than 48 hours, and no corrosion was observed. This indicates that the middle frame 100 of this application has good corrosion resistance.

[0089] Optionally, the copper salt comprises, by weight: 736.8 parts sodium chloride, 14,000 parts water, 0.005 to 0.03 parts glacial acetic acid, and 3.64 parts copper chloride.

[0090] Optionally, the middle frame 100 is subjected to a high temperature resistance time of 40 minutes or more in a vacuum environment at a temperature of 80°C.

[0091] Understandably, when the middle frame 100 is placed in a vacuum environment at 80°C for 40 minutes or more, the oxide film 20 of the middle frame 100 remains intact and does not peel off. This indicates that the middle frame 100 has good high-temperature resistance, the oxide film 20 has good adhesion, and it can withstand longer periods of use. The longer the high-temperature resistance time, the better the adhesion of the oxide film 20.

[0092] The middle frame 100 of this application embodiment can be prepared by the method described in the following embodiments of this application. In addition, it can also be prepared by other methods. The preparation method of this application embodiment is only one or more preparation methods of the middle frame 100 of this application and should not be construed as a limitation on the middle frame 100 provided in the embodiments of this application.

[0093] Please see Figure 3 This application embodiment also provides a method for preparing the middle frame 100, which includes:

[0094] S201, provides castings;

[0095] S202, the casting is shaped to obtain the first intermediate product;

[0096] S203, the first intermediate product is subjected to aging treatment to obtain a second intermediate product; wherein, the aging treatment includes a first-level aging treatment and a second-level aging treatment, the temperature of the second-level aging treatment being higher than the temperature of the first-level aging treatment; and

[0097] S204, the second intermediate product is anodized to obtain the middle frame 100, wherein the middle frame 100 includes a frame body 10 and an oxide film 20, the frame body 10 has a peripheral side surface 11, the oxide film 20 is disposed on the peripheral side surface 11 of the frame body 10, the yield strength of the frame body 10 is in the range of 480MPa to 510MPa, and the thickness of the oxide film 20 is in the range of 9.3μm to 12.1μm.

[0098] Specifically, the yield strength of the frame body 10 can be, but is not limited to, 480 MPa, 485 MPa, 490 MPa, 495 MPa, 500 MPa, 505 MPa, 510 MPa, etc. If the yield strength of the frame body 10 is too low, it is not conducive to making the middle frame 100 thinner; if the yield strength of the frame body 10 is too high, it is difficult to achieve the material for the middle frame 100, or if a material with a higher yield strength can be achieved, its corrosion resistance is low, making it difficult to achieve both corrosion resistance and other properties.

[0099] Specifically, the thickness of the oxide film 20 can be, but is not limited to, 9.3 μm, 9.5 μm, 9.8 μm, 10 μm, 10.3 μm, 10.5 μm, 10.8 μm, 11 μm, 11.3 μm, 11.5 μm, 11.8 μm, 12.0 μm, 12.1 μm, etc. If the oxide film 20 is too thin, the corrosion resistance of the middle frame 100 will be reduced; if the oxide film 20 is too thick, the risk of the oxide film 20 falling off when the middle frame 100 is subjected to external force will increase.

[0100] For a detailed description of other aspects of the middle frame 100, the frame body 10, and the oxide film 20, please refer to the description of the corresponding part of the above embodiments, which will not be repeated here.

[0101] The method for preparing the middle frame 100 in this embodiment involves forming a casting, followed by a two-stage aging treatment and anodizing. The two-stage aging treatment significantly improves the strength and corrosion resistance of the second intermediate product. This results in a slower growth rate of the oxide film 20 during anodizing, leading to a more uniform and denser oxide film. This, in turn, enhances the yield strength, corrosion resistance, and adhesion of the oxide film 20 to the frame body 10. Furthermore, the thinner and denser oxide film 20 improves the high-temperature stress resistance and adhesion of the middle frame 100, making it less prone to peeling and extending the service life of the middle frame 100.

[0102] In some embodiments, S201, providing the casting includes: providing a blank and homogenizing the blank to obtain the casting.

[0103] Optionally, the raw material composition of the blank includes, by mass fraction: 5.8% to 6.5% Zn (zinc), 2% to 2.5% Mg (magnesium), 0.1% to 0.5% Cu (copper), 0.1% to 0.3% Mn (manganese), 0.01% to 0.1% Si (silicon), 0.005% to 0.05% Ti (titanium), 0.01% to 0.2% Fe (iron), and the balance Al (aluminum).

[0104] Optionally, providing a blank includes: providing metal powder; and melting and casting the metal powder to obtain the blank.

[0105] In one specific embodiment, the blank is a rod with a diameter of 230 mm.

[0106] In this embodiment, by homogenizing the blank, the internal crystalline structure of the blank can be improved, the stress inside the blank can be eliminated, and the segregation of the blank can be reduced, thereby improving the extrusion performance of the blank. In addition, the size and uniformity of the grains in the formed casting can be better controlled, thereby improving the strength and corrosion resistance of the final middle frame 100.

[0107] Optionally, the homogenization process includes a three-stage homogenization process. The three-stage homogenization process better ensures sufficient solid solution of the low-melting-point phase, reduces the risk of overheating during the third stage of homogenization, and, due to the lower homogenization temperatures and smaller diffusion driving forces in the first two stages, better inhibits grain growth, resulting in better gloss and higher yield strength after anodizing, improving the appearance and yield strength of the middle frame 100. Furthermore, it also enhances the corrosion resistance of the middle frame 100.

[0108] Please see Figure 4 Optionally, the homogenization process includes:

[0109] S2011, The blank is kept at a temperature range of 300℃ to 330℃ for primary homogenization treatment;

[0110] Specifically, the temperature for the primary homogenization treatment can be, but is not limited to, 300℃, 305℃, 310℃, 315℃, 320℃, 325℃, 330℃, etc. If the temperature of the primary homogenization treatment is too low, the solute atoms diffuse slowly, and the low-melting-point precipitates (such as the η phase) are difficult to fully dissolve into the matrix, thus failing to achieve the homogenization effect. If the temperature of the primary homogenization treatment is too high, the low-melting-point phase may overheat at high temperatures, and the simultaneous diffusion of a large number of segregated solute atoms will reduce the diffusion efficiency, making the middle frame 100 obtained after anodizing prone to defects, including material streaks, reducing the appearance of the middle frame 100, and also reducing the yield strength of the middle frame 100.

[0111] Optionally, the heat preservation time for primary homogenization is 1 hour to 3 hours. Specifically, the heat preservation time for primary homogenization can be, but is not limited to, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc. In this embodiment, if the heat preservation time for primary homogenization is too short, homogenization will be insufficient, reducing the yield strength and corrosion resistance of the middle frame 100; if the heat preservation time for primary homogenization is too long, energy consumption will increase, increasing the production cost of the middle frame 100.

[0112] S2012, the blank is held at a temperature range of 400℃ to 420℃ for a two-stage homogenization process; and

[0113] Specifically, the temperature for the secondary homogenization treatment can be, but is not limited to, 400℃, 403℃, 405℃, 408℃, 410℃, 413℃, 415℃, 418℃, 420℃, etc. If the temperature of the secondary homogenization treatment is too low, the solute atoms diffuse slowly, and the low-melting-point precipitates (such as the η phase) are difficult to fully dissolve into the matrix, thus failing to achieve the homogenization effect. If the temperature of the secondary homogenization treatment is too high, the low-melting-point phase may overheat at high temperatures, and the simultaneous diffusion of a large number of segregated solute atoms will reduce the diffusion efficiency, making the middle frame 100 obtained after anodizing prone to defects, including material streaks, reducing the appearance of the middle frame 100, and also reducing the yield strength of the middle frame 100.

[0114] Optionally, the heat preservation time for secondary homogenization is 2 hours to 6 hours. Specifically, the heat preservation time for secondary homogenization can be, but is not limited to, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc. In this embodiment, if the heat preservation time for secondary homogenization is too short, the homogenization will be insufficient, reducing the yield strength and corrosion resistance of the middle frame 100; if the heat preservation time for secondary homogenization is too long, it will increase energy consumption and increase the production cost of the middle frame 100.

[0115] S2013, the blank is kept at a temperature range of 500℃ to 530℃ for three-stage homogenization treatment.

[0116] Specifically, the temperature for the three-stage homogenization process can be, but is not limited to, 500℃, 503℃, 505℃, 508℃, 510℃, 513℃, 515℃, 518℃, 520℃, 523℃, 525℃, 528℃, and 530℃. In this embodiment, if the temperature of the three-stage homogenization is too low, it will affect the elimination of high-melting-point phases such as the S phase and β phase, reducing the yield strength and corrosion resistance of the resulting middle frame 100; if the temperature of the three-stage homogenization is too high, overheating is likely to occur, which will also reduce the yield strength and corrosion resistance of the middle frame 100.

[0117] Optionally, the holding time for three-stage homogenization is 6 to 10 hours. Specifically, the holding time for three-stage homogenization can be, but is not limited to, 6 hours, 7 hours, 8 hours, 9 hours, and 10 hours. If the holding time for three-stage homogenization is too short, elemental segregation will not be significantly improved, homogenization will be insufficient, and coarse iron-containing phases may still be continuously distributed along the grain boundaries, which is not sufficiently dispersed, thus affecting the mechanical and corrosion resistance of the middle frame 100. If the holding time for three-stage homogenization is too long, energy consumption will increase, the risk of overheating will increase, and grain growth will also occur. All of these factors reduce the yield strength and corrosion resistance of the middle frame 100.

[0118] Optionally, after the three-stage homogenization process, the homogenization process further includes cooling. For example, air cooling is used to bring the temperature to room temperature.

[0119] Optionally, the cooling rate after three-stage homogenization ranges from 250℃ / h to 300℃ / h. Specifically, the cooling rate after three-stage homogenization can be, but is not limited to, 250℃ / h, 260℃ / h, 270℃ / h, 280℃ / h, 290℃ / h, 300℃ / h, etc.

[0120] Please see Figure 5 In some embodiments, in S202, the step of molding the casting to obtain a first intermediate product includes:

[0121] S2021, after preheating the casting at a temperature of 470°C to 490°C, it is extruded and the temperature of the extrusion outlet is set to 500°C to 530°C; and

[0122] Understandably, the temperature at the extrusion exit is higher than the preheating temperature of the casting. This better ensures that the T phase and η phase are fully dissolved into the matrix.

[0123] Optionally, the casting is preheated at 470°C to 490°C for 1 to 3 hours (e.g., 1 hour, 2 hours, 3 hours) and then extruded on an extruder to obtain a first intermediate product. The extrusion speed ranges from 2 m / min to 5 m / min (e.g., 2 m / min, 3 m / min, 4 m / min, 5 m / min, etc.), and the product exit temperature (i.e., the extrusion outlet temperature) is controlled at 500°C to 530°C. In this embodiment, a slower extrusion speed ensures better surface quality of the product.

[0124] Specifically, the preheating temperature of the casting can be, but is not limited to, 470℃, 475℃, 480℃, 485℃, 490℃, etc.

[0125] Specifically, the temperature at the extrusion outlet can be, but is not limited to, 500℃, 505℃, 510℃, 515℃, 520℃, 525℃, 530℃, etc.

[0126] S2022, quenching treatment is performed at a cooling rate of 40℃ / s to 60℃ / s to obtain the first intermediate product.

[0127] Optionally, the extruded product is cooled by online quenching, that is, after extrusion, the product is directly placed into a room temperature water bath at 20°C to 25°C for water cooling, with a cooling rate of 40°C / s to 60°C / s.

[0128] Specifically, the cooling rate can be, but is not limited to, 40℃ / s, 45℃ / s, 50℃ / s, 55℃ / s, 60℃ / s, etc. A cooling rate that is too slow will cause the supersaturated solid solution to decompose, thereby reducing the strength of the second intermediate product obtained after aging; a cooling rate that is too fast may cause the extruded first intermediate product to undergo significant deformation due to internal stress.

[0129] In this embodiment, a faster quenching rate can ensure the formation of a supersaturated solid solution, which provides a driving force for the generation of a large number of dispersed fine precipitate strengthening phases during the subsequent aging process. At the same time, the cooling rate cannot be too fast, otherwise the first intermediate product is prone to deformation.

[0130] In some embodiments, in S203, the first-level aging treatment includes performing a first-level aging treatment at a temperature of 120°C to 130°C.

[0131] Specifically, the temperature for the first-stage aging treatment can be, but is not limited to, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃, and 130℃. If the temperature of the first-stage aging treatment is too low, there may not be enough driving force to generate uniform and fine precipitated strengthening phases, which reduces the yield strength of the second intermediate product and the yield strength and wear resistance of the middle frame 100. If the temperature of the first-stage aging treatment is too high, the precipitated strengthening phases may grow rapidly in a short period of time, making it difficult to control the size of the precipitated strengthening phases, thereby reducing the yield strength of the second intermediate product and the middle frame 100.

[0132] Optionally, the primary aging treatment time is 20 to 24 hours. Specifically, the primary aging treatment time can be, but is not limited to, 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, etc. If the primary aging treatment time is too short, there will be fewer precipitated strengthening phases distributed in the matrix, resulting in a reduction of non-uniform nucleation sites during the secondary aging treatment, thus reducing the mechanical properties of the second intermediate product and the middle frame 100. If the primary aging treatment time is too long, the size of the precipitated strengthening phase will be too large, thus reducing the yield strength of the second intermediate product and the middle frame 100.

[0133] Optionally, after the first intermediate product undergoes primary aging treatment, the average size of the precipitated strengthening phase ranges from 3 nm to 8 nm. Specifically, after the first intermediate product undergoes primary aging treatment, the average size of the precipitated strengthening phase can be, but is not limited to, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, etc. If the average particle size of the precipitated strengthening phase is too small, the corrosion resistance of the frame body 10 and the oxide film 20 is improved, but the yield strength of the frame body 10 is reduced; if the average particle size of the precipitated strengthening phase is too large, the yield strength of the frame body 10 is improved, but the corrosion resistance of the frame body 10 and the oxide film 20 is reduced.

[0134] Optionally, after the first intermediate product undergoes primary aging treatment, the average size of the grain boundary phase ranges from 15 nm to 25 nm. Specifically, after the first intermediate product undergoes primary aging treatment, the average size of the grain boundary phase can be, but is not limited to, 15 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 25 nm, etc. If the average size of the grain boundary phase is too small, the spacing between the grain boundary phases is small, reducing the corrosion resistance of the middle frame 100; if the average size of the grain boundary phase increases, the spacing between the grain boundary phases increases, increasing the corrosion resistance of the middle frame 100, but if the average size of the grain boundary phase is too large, it increases the difficulty of fabricating the frame body 10.

[0135] Optionally, after the first intermediate product undergoes primary aging treatment, the spacing between two adjacent grain boundary phases ranges from 5 nm to 15 nm. Specifically, after the first intermediate product undergoes primary aging treatment, the spacing between two adjacent grain boundary phases can be, but is not limited to, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 15 nm, etc. If the spacing between two adjacent grain boundary phases is too small, the corrosion resistance of the middle frame 100 is reduced; increasing the spacing between two adjacent grain boundary phases can improve the corrosion resistance of the middle frame 100, but increases the difficulty of fabricating the frame body 10.

[0136] Optionally, the yield strength of the first intermediate product after primary aging treatment ranges from 500 MPa to 520 MPa. Specifically, the yield strength of the first intermediate product after primary aging treatment can be, but is not limited to, 500 MPa, 505 MPa, 510 MPa, 515 MPa, 520 MPa, etc. If the yield strength of the first intermediate product after primary aging treatment is too low, it is not conducive to making the middle frame 100 thinner; if the yield strength of the first intermediate product after primary aging treatment is too high, it is difficult to achieve the material requirements for the middle frame 100, or the material that can achieve a higher yield strength has lower corrosion resistance, making it difficult to simultaneously possess corrosion resistance.

[0137] In some embodiments, in S203, the secondary aging process includes performing a secondary aging process at a temperature of 150°C to 160°C.

[0138] Specifically, the temperature for the secondary aging treatment can be, but is not limited to, 150℃, 151℃, 152℃, 153℃, 154℃, 155℃, 156℃, 157℃, 158℃, 159℃, and 160℃. If the temperature for the secondary aging treatment is too low, the solute atoms will not have sufficient diffusion driving force, making it difficult for the precipitated phase to grow and polymerize, resulting in an insufficiently discontinuous distribution of the grain boundary precipitates and reducing the corrosion resistance of the second intermediate product and the middle frame 100. If the temperature for the secondary aging treatment is too high, the precipitates may grow rapidly, making it difficult to control their size and distribution. In addition, if the temperature for the secondary aging treatment is too high, the precipitates may re-dissolve into the matrix, significantly reducing the strength of the second intermediate product and the middle frame 100.

[0139] Optionally, the secondary aging treatment time is 5 to 7 hours. Specifically, the secondary aging treatment time can be, but is not limited to, 5 hours, 5.5 hours, 6 hours, 6.5 hours, and 7 hours. If the secondary aging treatment time is too short, a large number of solute atoms will remain in the matrix, which is not conducive to improving the corrosion resistance of the second intermediate product; if the secondary aging treatment time is too long, it will cause the precipitated strengthening phase inside the grain to grow excessively and merge, significantly reducing the strength of the second intermediate product and the middle frame 100.

[0140] Optionally, the yield strength of the second intermediate product ranges from 480 MPa to 510 MPa. Specifically, the yield strength of the second intermediate product can be, but is not limited to, 480 MPa, 485 MPa, 490 MPa, 495 MPa, 500 MPa, 505 MPa, 510 MPa, etc. If the yield strength of the second intermediate product is too low, it is not conducive to making the middle frame 100 thinner; if the yield strength of the second intermediate product is too high, it is difficult to achieve the material for the middle frame 100, or the material that can achieve a higher yield strength has lower corrosion resistance, making it difficult to achieve both corrosion resistance and other properties.

[0141] Optionally, the average particle size of the precipitated strengthening phase of the second intermediate product ranges from 10 nm to 20 nm. Specifically, the average particle size of the precipitated strengthening phase of the second intermediate product can be, but is not limited to, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, etc. If the average particle size of the precipitated strengthening phase of the second intermediate product is too small, the corrosion resistance of the second intermediate product and the middle frame 100 is improved, but the yield strength of the second intermediate product and the middle frame 100 is reduced; if the average particle size of the precipitated strengthening phase of the second intermediate product is too large, the yield strength of the second intermediate product and the middle frame 100 is improved, but the corrosion resistance of the second intermediate product and the middle frame 100 is reduced.

[0142] Optionally, the average size of the grain boundary phase in the second intermediate product ranges from 30 nm to 50 nm. Specifically, the average size of the grain boundary phase in the second intermediate product can be, but is not limited to, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, 48 nm, 50 nm, etc. In this embodiment, if the average size of the grain boundary phase in the second intermediate product is too small, the spacing between the grain boundary phases is small, which reduces the corrosion resistance of the second intermediate product and the middle frame 100; if the average size of the grain boundary phase in the second intermediate product increases, the spacing between the grain boundary phases increases, which increases the corrosion resistance of the second intermediate product and the middle frame 100, but if the average size of the grain boundary phase is too large, it increases the difficulty of preparing the second intermediate product.

[0143] Optionally, the spacing between two adjacent grain boundary phases on the second intermediate product ranges from 30 nm to 60 nm. Specifically, the spacing between two adjacent grain boundary phases on the second intermediate product can be, but is not limited to, 30 nm, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, 48 nm, 50 nm, 52 nm, 54 nm, 56 nm, 58 nm, 60 nm, etc. In this embodiment, if the spacing between two adjacent grain boundary phases on the second intermediate product is too small, the corrosion resistance of the middle frame 100 is reduced; increasing the spacing between two adjacent grain boundary phases on the second intermediate product can improve the corrosion resistance of the middle frame 100, but it increases the difficulty of preparing the second intermediate product.

[0144] Optionally, the number density of the second phase ranges from 0.9 × 10⁻⁶. 4 μm -2 Up to 8.7×10 4 μm -2 Specifically, the number density of the second phase can be, but is not limited to, 0.9 × 10⁻⁶. 4 μm -2 1.0×10 4 μm -2 1.1×10 4 μm -2 1.3×10 4 μm -2 1.5×10 4 μm -2 2×10 4 μm -2 3×10 4 μm -2 4×10 4 μm -2 5×10 4 μm -2 6×104 μm -2 7×10 4 μm -2 8×10 4 μm -2 8.5×10 4 μm -2 8.7×10 4 μm -2 In this embodiment, if the quantity density of the second phase is too low, the yield strength of the frame body 10 will be too low. If the quantity density of the second phase is too high, since the oxide film 20 is obtained by anodizing the frame body 10, the corrosion resistance of the middle frame 100 will be reduced.

[0145] In this embodiment, a first-stage aging treatment is first performed to generate a high-density MgZn2 precipitate strengthening phase in the matrix of the first intermediate product. Figure 6 As shown), but at this time the second phase on the grain boundary is more continuous (as shown). Figure 7 As shown), the solid solution also contains a large number of Mg and Zn solute atoms, resulting in relatively poor corrosion resistance of the matrix; after secondary aging treatment, the secondary aging treatment has a higher driving force, and the precipitation strengthening phase inside the grains merges and grows (as shown). Figure 8 As shown), it consumes a large number of Mg and Zn solute atoms in the solid solution, and the distribution of the second phase at the grain boundaries is more discontinuous. Figure 9 As shown in the figure, this improves the corrosion resistance of the second intermediate product and the middle frame 100.

[0146] In some embodiments, in S204, the step of anodizing the second intermediate product to obtain the middle frame 100 includes: placing the second intermediate product in a sulfuric acid solution with a temperature of 12°C to 18°C ​​and a concentration of 180 g / L to 220 g / L for anodizing, with an oxidation voltage of 11 V to 15 V, to obtain the middle frame 100.

[0147] Please see Figure 10 Furthermore, the second intermediate product is anodized, including:

[0148] S2041, Polishing and cleaning the second intermediate product;

[0149] Optionally, polishing and cleaning the second intermediate product includes:

[0150] (1) Grinding and polishing: Use sandpaper to grind the surface of the second intermediate product until it is smooth, and then mechanically polish the second intermediate product;

[0151] (2) Degreasing and cleaning: Degreasing is performed in a degreasing solution for 3 to 8 minutes (e.g., 3 min, 4 min, 5 min, 6 min, 7 min, 8 min) at a temperature of 70°C to 90°C (e.g., 70°C, 75°C, 80°C, 85°C, 90°C, etc.), followed by rinsing with purified water; and

[0152] (3) Degreasing and cleaning: Degreasing treatment is carried out in degreasing solution for 30s to 300s (e.g., 30s, 50s, 80s, 100s, 150s, 200s, 250s, 300s, etc.) and at a temperature of 40℃ to 60℃ (e.g., 40℃, 45℃, 50℃, 55℃, 60℃, etc.); then clean with pure water.

[0153] S2042, the second intermediate product is anodized in a sulfuric acid solution with a temperature of 12°C to 18°C ​​and a concentration of 180 g / L to 220 g / L, at an oxidation voltage of 11 V to 15 V; and

[0154] Specifically, the anodizing temperature can be, but is not limited to, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, etc.

[0155] Specifically, the concentration of the sulfuric acid solution can be, but is not limited to, 180 g / L, 185 g / L, 190 g / L, 195 g / L, 200 g / L, 205 g / L, 210 g / L, 215 g / L, 220 g / L, etc. Lower concentrations of sulfuric acid can result in a smoother, denser, and more uniform oxide film 20, but reduce oxidation efficiency and increase the preparation cost of the middle frame 100. Increased sulfuric acid concentration leads to increased surface roughness of the oxide film 20, making it more porous and reducing the corrosion resistance of the middle frame 100.

[0156] Specifically, the oxidation voltage can be, but is not limited to, 11V, 12V, 13V, 14V, 15V, etc. Lower voltages result in a denser and more uniform oxide film 20, but reduce oxidation efficiency and increase the manufacturing cost of the middle frame 100; higher voltages result in a more porous oxide film 20 with an uneven surface, reducing the corrosion resistance of the middle frame 100.

[0157] Optionally, the anodizing time is between 1200s and 4200s. Further, the anodizing time is between 1800s and 3600s. Specifically, the anodizing time can be, but is not limited to, 1800s, 2000s, 2200s, 2400s, 2600s, 2800s, 3000s, 3200s, 3400s, and 3600s. If the anodizing time is too short, the oxide film 20 will be too thin, reducing the corrosion resistance of the middle frame 100; if the anodizing time is too long, the oxide film 20 will be too thick, increasing the risk of oxide film 20 peeling off.

[0158] S2043 is washed, colored and sealed to obtain the middle frame 100.

[0159] Optionally, after anodizing, the product undergoes ultrasonic water washing to remove residual acid. Next, it is immersed in a dyeing bath to allow dye molecules to penetrate the oxide pores, completing the coloring process; then, it is washed with water to remove excess dye from the surface. A standard aluminum alloy oxide film sealing solution (20) is used for sealing; then, it is washed with water to remove any residual chemicals from the surface.

[0160] In this embodiment, the second intermediate product is anodized, thereby oxidizing the surface material (such as aluminum) of the second intermediate product into an oxide film 20 (e.g., a porous alumina film). The unoxidized portion of the second intermediate product forms the frame body 10, thus giving the resulting middle frame 100 good yield strength and high corrosion resistance. Furthermore, after anodizing, coloring and sealing are performed, allowing the middle frame 100 to have various colors and a good appearance.

[0161] The middle frame 100 of this application will be further described below through specific embodiments.

[0162] Examples 1 to 7

[0163] The middle frame 100 of each embodiment is prepared by the following steps:

[0164] (1) A blank is provided, wherein the raw material composition of the blank comprises, by mass fraction: 6% Zn, 2.3% Mg, 0.3% Cu, 0.12% Mn, 0.05% Si, 0.03% Ti, 0.1% Fe and the balance Al;

[0165] (2) The billet is kept at a temperature of 320℃ for a first-level homogenization treatment for 2 hours; the billet is kept at a temperature of 410℃ for a second-level homogenization treatment for 4 hours; and the billet is kept at a temperature of 515℃ for a third-level homogenization treatment for 8 hours to obtain the casting.

[0166] (3) The casting is preheated at 480°C and then extruded at a speed of 3m / min, with the temperature of the extrusion outlet being 515°C; the casting is then quenched at a cooling rate of 50°C / s to obtain the first intermediate product.

[0167] (4) The first intermediate product is subjected to a first-stage aging treatment at a temperature of 130°C for 22 hours.

[0168] (5) The first intermediate product is subjected to a second-stage aging treatment at a temperature of 160°C for 6 hours to obtain the second intermediate product.

[0169] (6) Use sandpaper to smooth the surface of the second intermediate product, and then mechanically polish it; degrease it in a degreasing solution for 5 minutes at a temperature of 80°C; then clean it with pure water; degrease it in an oil-removing solution for 200 seconds at a temperature of 50°C, and then clean it with pure water.

[0170] (7) The second intermediate product was anodicly oxidized in a sulfuric acid solution with a temperature of 15°C and a concentration of 200 g / L. The oxidation voltage was 13 V. The oxidation time of each embodiment is shown in Table 1 below.

[0171] (8) Perform ultrasonic water washing, coloring and sealing to obtain the middle frame 100.

[0172] Comparative Examples 1 to 7

[0173] The middle frame 100 of each comparative example is prepared by the following steps:

[0174] (1) A blank is provided, wherein the raw material composition of the blank comprises, by mass fraction: 6% Zn, 2.3% Mg, 0.3% Cu, 0.12% Mn, 0.05% Si, 0.03% Ti, 0.1% Fe and the balance Al;

[0175] (2) The billet is kept at a temperature of 320℃ for a first-stage homogenization treatment for 2 hours; the billet is kept at a temperature of 410℃ for a second-stage homogenization treatment for 4 hours; the billet is kept at a temperature of 515℃ for a third-stage homogenization treatment for 8 hours, to obtain the casting.

[0176] (3) The casting is preheated at 480°C and then extruded at a speed of 3m / min, with the temperature of the extrusion outlet being 515°C; the casting is then quenched at a cooling rate of 50°C / s to obtain the first intermediate product.

[0177] (4) The first intermediate product is subjected to a first-stage aging treatment at a temperature of 130°C for 22 hours to obtain the second intermediate product.

[0178] (5) Use sandpaper to smooth the surface of the second intermediate product, and then mechanically polish it; degrease it in a degreasing solution for 5 minutes at a temperature of 80°C; then clean it with pure water; degrease it in an oil-removing solution for 200 seconds at a temperature of 50°C, and then clean it with pure water.

[0179] (6) The second intermediate product was anodicly oxidized in a sulfuric acid solution with a temperature of 15°C and a concentration of 200 g / L. The oxidation voltage was 13 V. The oxidation times of each comparative example are shown in Table 2 below.

[0180] (7) Perform ultrasonic water washing, coloring and sealing to obtain the middle frame 100.

[0181] The performance of the mid-frames 100 prepared in Examples 1 to 7 and Comparative Examples 1 to 7 was tested, and the test results are shown in Tables 1 and 2 below.

[0182] (1) Copper salt fume corrosion test: The middle frame 100 of each embodiment and comparative example was corroded in copper salt fume at 25°C and pH value of 3.0 to 3.1 for 48 hours, and the corrosion condition of the middle frame 100 was recorded. The copper salt, by weight, included: 736.8g sodium chloride, 14000g water, 0.02g glacial acetic acid and 3.64g copper chloride.

[0183] (2) High temperature stress test: The middle frame 100 is placed in a vacuum environment at 80°C for 40 minutes, and the oxide film 20 is observed to fall off.

[0184] (3) Thickness of oxide film 20: obtained by taking a photo of the end face of the middle frame 100 using an optical microscope.

[0185] Table 1 Test data of the middle frame 100 in Examples 1 to 7

[0186]

[0187] Table 2 Test data for the middle frame 100 of Comparative Examples 1 to 7

[0188]

[0189] As shown in Table 1, the thickness of the oxide film 20 on the middle frame 100 gradually increases with increasing oxidation time. The corrosion resistance of the oxide film 20 gradually improves, but its high-temperature resistance (adhesion) decreases. However, the middle frames 100 of Examples 1 to 7 can all withstand 48 hours of copper salt fume corrosion. After 48 hours of copper salt fume corrosion, the middle frame 100 still shows no signs of corrosion, indicating that the copper salt fume corrosion resistance time of the middle frames 100 in Examples 1 to 7 is greater than or equal to 48 hours. Furthermore, the oxide film 20 of the middle frames 100 in Examples 1 to 6 did not experience any peeling, while the oxide film 20 of Example 7 did peel off. This indicates that when the thickness of the oxide film 20 on the middle frame 100 in this application is between 9.3 μm and 12.1 μm, the middle frame 100 can have higher corrosion resistance while also exhibiting better adhesion and higher high-temperature resistance. This indicates that two-stage aging can significantly improve the corrosion and peeling of the oxide film 20 on the middle frame 100 under low copper content conditions.

[0190] As shown in Table 2, the thickness of the oxide film 20 on the middle frame 100 gradually increases with oxidation time. The corrosion resistance of the oxide film 20 gradually improves, but its high-temperature resistance (adhesion) gradually decreases. The oxide film 20 on the middle frames 100 of Comparative Examples 1 to 3 is relatively thin, and corrosion occurred before 48 hours in the copper salt spray test, but the oxide film 20 did not peel off in the high-temperature resistance test. The middle frame 100 of Comparative Example 4 also failed to meet the requirements in both the copper salt spray corrosion test and the high-temperature resistance test. The middle frames 100 of Comparative Examples 5 to 7 were not corroded after 48 hours in the copper salt spray test, exhibiting good corrosion resistance. However, due to the excessive thickness of the oxide film 20, they all peeled off before reaching the preset time in the high-temperature resistance test. The test results of Comparative Examples 1 to 7 indicate that the first-level aging method is insufficient to balance the high corrosion resistance and good adhesion of the oxide film 20.

[0191] Furthermore, the test results from Examples 1 to 7 and Comparative Examples 1 to 7 show that, under the same oxidation time, compared with the single-stage aging scheme in the comparative examples, the oxide film 20 of the middle frame 100 obtained by the double-stage aging in the examples is thinner, but has better corrosion resistance and high temperature resistance (adhesion). This indicates that the oxide film 20 of the middle frame 100 obtained by the scheme of this application is more dense and has higher corrosion resistance and better adhesion.

[0192] Transmission electron microscopy (TEM) images of the crystal interior after first-stage aging of the first intermediate states of Examples 1 to 7 are shown below. Figure 6 As shown. Transmission electron microscopy (TEM) images of the grain boundaries after first-order aging of the first intermediate states in Examples 1 to 7 are shown below. Figure 7As shown. Transmission electron microscopy (TEM) images of the inner crystal of the second intermediate products (i.e., after secondary aging) from Examples 1 to 7 are shown below. Figure 8 As shown. Transmission electron microscopy (TEM) images of the grain boundaries of the second intermediate products (i.e., after secondary aging) from Examples 1 to 7 are shown below. Figure 9 As shown. By Figures 6 to 9 It can be seen that after the second-stage aging treatment, the second-stage aging treatment has a higher driving force, the precipitation strengthening phase inside the grain merges and grows, consumes a large number of Mg and Zn solute atoms in the solid solution, and the distribution of the second phase on the grain boundary is more discontinuous, thereby improving the corrosion resistance of the second intermediate product and the middle frame 100.

[0193] Figure 11 This is an optical microscope image of the cross-section of the middle frame 100 of Example 1. Figure 12 This is an optical microscope image of the cross-section of the middle frame 100 in Comparative Example 1. (From...) Figure 11 and Figure 12 It can be seen that the oxide film 20 of Example 1 is thinner, while the oxide film 20 of Comparative Example 1 is thicker. This indicates that the second intermediate product obtained after the two-stage aging treatment forms the oxide film 20 more slowly during the anodizing process, and the formed oxide film 20 is more uniform, denser, and has better corrosion resistance and adhesion.

[0194] Examples 8 to 15, Comparative Example 8

[0195] The differences between each embodiment and comparative example and embodiment 4 lie in the time or temperature of the first-stage aging or the time or temperature of the second-stage aging, as shown in Table 3 below.

[0196] Table 3 Test data of the middle frame 100 of Examples 4, 8 to 15, and Comparative Example 8

[0197]

[0198] As can be seen from the test results in Table 3, the middle frame 100 of each embodiment and comparative example of this application has high corrosion resistance, good high temperature resistance, and the oxide film 20 is less likely to peel off.

[0199] The test results of Examples 4, 8, 9 and Comparative Example 8 show that when the temperature of the first-stage aging is too low, the thickness of the oxide film 20 will be reduced, which may reduce the corrosion resistance of the middle frame 100.

[0200] Please see Figures 13 to 15This application also provides an electronic device 300, which includes a display screen 310, a mid-frame 100 as described in this application embodiment, and a processor 330. The mid-frame 100 is used to support the display screen 310, and the processor 330 is supported on the mid-frame 100. The processor 330 is electrically connected to the display screen 310 and is used to control the display screen 310 to display.

[0201] The electronic device 300 in this application embodiment can be, but is not limited to, a mobile phone, tablet computer, laptop computer, desktop computer, smart bracelet, smartwatch, e-reader, game console, or other portable electronic device 300.

[0202] For a detailed description of the middle frame 100, please refer to the description of the corresponding part of the above embodiment, which will not be repeated here.

[0203] Optionally, the display screen 310 may be, but is not limited to, one or more of the following: liquid crystal display screen, light-emitting diode display screen (LED display screen), micro light-emitting diode display screen (Micro LED display screen), mini LED display screen, organic light-emitting diode display screen (OLED display screen).

[0204] Optionally, processor 330 includes one or more general-purpose processors, wherein the general-purpose processor can be any type of device capable of processing electronic instructions, including a central processing unit (CPU), microprocessor, microcontroller, main processor, controller, and ASIC, etc. Processor 330 is used to execute various types of digital storage instructions, such as software or firmware programs stored in memory, which enables the computing device to provide a wide range of services.

[0205] Optionally, the electronic device 300 of this application further includes a memory 350. The memory 350 is electrically connected to the processor 330 and is used to store the program code required for the processor 330 to run, the program code required to control the display screen 310, the display content of the display screen 310, etc.

[0206] Optionally, memory 350 may include volatile memory, such as random access memory (RAM); memory 350 may also include non-volatile memory (NVM), such as read-only memory (ROM), flash memory (FM), hard disk drive (HDD), or solid-state drive (SSD). Memory 350 may also include combinations of the above types of memory.

[0207] In some embodiments, the electronic device 300 of this application further includes a housing and a camera module 370. The housing 340 is disposed on the side of the mid-frame 100 opposite to the display screen 310, and the side of the mid-frame 100 is exposed between the housing 340 and the display screen 310. The mid-frame 100 and the housing 340 enclose an accommodating space (not shown), which is used to accommodate the processor 330, the memory 350, and the camera module 370. The camera module 370 is electrically connected to the processor 330 and is used to take pictures under the control of the processor 330.

[0208] Optionally, the housing 340 has a light-transmitting portion 341, through which the camera module 370 can capture images. That is, in this embodiment, the camera module 370 is a rear-facing camera module 370. It is understood that in other embodiments, the light-transmitting portion 341 may be disposed on the display screen 310, i.e., the camera module 370 is a front-facing camera module 370. In the schematic diagram of this embodiment, the light-transmitting portion 341 is shown as an opening. In other embodiments, the light-transmitting portion 341 may not be an opening, but may be made of a light-transmitting material, such as plastic or glass.

[0209] It is understood that the electronic device 300 described in this embodiment is merely one form of the electronic device 300 used in the middle frame 100, and should not be construed as a limitation on the electronic device 300 provided in this application, nor should it be construed as a limitation on the middle frame 100 provided in various embodiments of this application.

[0210] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form yet another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0211] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A middle frame, characterized in that, include: The frame body has circumferential surfaces, and the yield strength of the frame body ranges from 480 MPa to 510 MPa. as well as An oxide film is disposed on the peripheral side surface of the frame body, and the thickness of the oxide film ranges from 9.3 μm to 12.1 μm.

2. The middle frame according to claim 1, characterized in that, The frame body is made of aluminum alloy, which includes grains and a second phase. The second phase includes a precipitation strengthening phase and a grain boundary phase. The precipitation strengthening phase is distributed within the grains, and the grain boundary phase is distributed at the grain boundaries. The average particle size of the precipitation strengthening phase ranges from 10 nm to 20 nm.

3. The middle frame according to claim 2, characterized in that, The average size of the grain boundary phase ranges from 30 nm to 50 nm.

4. The middle frame according to claim 2, characterized in that, The spacing between two adjacent grain boundary phases ranges from 30 nm to 60 nm.

5. The middle frame according to claim 2, characterized in that, The number density of the second phase ranges from 0.9 × 10⁻⁶. 4 μm -2 Up to 8.7×10 4 μm -2 .

6. The middle frame according to claim 1, characterized in that, The raw material components of the frame body, by mass fraction, include: 5.8% to 6.5% Zn, 2% to 2.5% Mg, 0.1% to 0.5% Cu, 0.1% to 0.3% Mn, and the balance Al.

7. The middle frame according to any one of claims 1-6, characterized in that, The Vickers hardness of the oxide film ranges from 300 HV to 450 HV.

8. The middle frame according to claim 1, characterized in that, The yield strength of the frame body ranges from 490 MPa to 510 MPa.

9. A method for preparing a middle frame, characterized in that, include: Provide castings; The casting is molded to obtain a first intermediate product; The first intermediate product is subjected to aging treatment to obtain a second intermediate product; wherein the aging treatment includes a first-level aging treatment and a second-level aging treatment, the temperature of the second-level aging treatment being higher than the temperature of the first-level aging treatment; and The second intermediate product is anodized to obtain the middle frame, wherein the middle frame includes a frame body and an oxide film, the frame body has a peripheral side surface, the oxide film is disposed on the peripheral side surface of the frame body, the yield strength of the frame body is in the range of 480 MPa to 510 MPa, and the thickness of the oxide film is in the range of 9.3 μm to 12.1 μm.

10. The method for preparing the middle frame according to claim 9, characterized in that, The provided castings include: A blank is provided, and the blank is homogenized to obtain the casting; The homogenization process includes: The blank is kept at a temperature range of 300℃ to 330℃ for primary homogenization treatment. The blank is held at a temperature range of 400℃ to 420℃ for a two-stage homogenization process; and The blank is kept at a temperature range of 500℃ to 530℃ for three-stage homogenization treatment.

11. The method for preparing the middle frame according to claim 9, characterized in that, The first-level aging treatment includes: performing a first-level aging treatment at a temperature of 120°C to 130°C; The secondary aging process includes performing a secondary aging process at a temperature of 150°C to 160°C.

12. The method for preparing the middle frame according to claim 9, characterized in that, The process of molding the casting to obtain a first intermediate product includes: The casting is preheated at a temperature of 470°C to 490°C, then extruded, with the extrusion outlet temperature set at 500°C to 530°C; and The first intermediate product is obtained by quenching at a cooling rate of 40°C / s to 60°C / s.

13. The method for preparing the middle frame according to any one of claims 9-12, characterized in that, The step of anodizing the second intermediate product to obtain the middle frame includes: The second intermediate product was placed in a sulfuric acid solution with a temperature of 12°C to 18°C ​​and a concentration of 180 g / L to 220 g / L for anodizing at an oxidation voltage of 11 V to 15 V to obtain the middle frame.

14. The method for preparing the middle frame according to claim 13, characterized in that, The anodizing time is from 1200s to 4200s.

15. An electronic device, characterized in that, include: Display screen; A mid-frame as described in any one of claims 1-8 or a mid-frame prepared by any one of claims 9-13, wherein the mid-frame is used to support the display screen; and A processor is mounted on the mid-frame and electrically connected to the display screen for controlling the display screen to perform a display.

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